The Act of Accord (39 Hen. 6) was an act of the Parliament of England. It was passed on 25 October 1460 during a period of intense political division and partisanship at the top of government. Three weeks earlier, Richard, Duke of York had entered the Council Chamber—in the presence of several lords—and laid his hand on the empty throne, claiming the crown of England. His grounds were that he and King Henry VI were both direct descendants of Edward III, but York possessed two claims, through both the male and female lines, and Henry's was through only one. Following discussions between royal justices, York and Parliament, the House of Lords decided that Henry was to retain the crown for life, but York and his heirs were to succeed him. This automatically removed Henry's son, Edward, Prince of Wales, from the succession. Henry agreed to the compromise, which became the Act of Accord.

Political partisanship had already erupted into civil war the year before and, far from lowering political pressure, the act split the nobility further. Although Henry had publicly supported the act, Queen Margaret of Anjou refused to accept the disinheritance of their son. In this, she was joined by the majority of the English nobility, who also opposed York. King Henry, nominally the head of state, was still in London, which was controlled by the Yorkist government. Margaret, on the other hand, was in the north with her son, raising an army. This began the systematic destruction of York's and the Nevilles' Yorkshire estates. York led an army to challenge her but was killed at the Battle of Wakefield on 30 December. The Lancastrians, in turn, were defeated three months later at the Battle of Towton by York's son, who was crowned King Edward IV on 28 June 1461.

Throughout the 1450s, English politics became partisan and factional. Richard, Duke of York, a powerful noble and heir to the throne until 1453—when Margaret had a son—opposed King Henry VI's government. Henry was easily influenced by favourites, particularly Edmund, Duke of Somerset. In August 1453, Henry had a nervous breakdown; comatose, unable to feed himself or recognise people, the House of Lords appointed the Duke of York Protector of the Realm. This office was effectively a resurrection of that which Humphrey, Duke of Gloucester and John, Duke of Bedford had held during the minority of Henry VI. It was decidedly limited in its powers—the Protector's authority was constrained by the council, which oversaw it. The lords favoured York for the position by way of being the King's closest adult kinsman, as had his predecessors, Gloucester and Bedford, been to Henry V. York and his allies, the powerful northern Neville family—Richard, Earl of Salisbury and his son, Richard, Earl of Warwick—now ran the government. Somerset was imprisoned for treason.

During this period, strong kings were seen as essential to sound governance and peace, but weak government led to disorder. Contemporaries attributed the rise in violence and feuding to the King's weakness. The violence between the Percys and Nevilles in Yorkshire was of such breadth that it impacted with government, and a chronicler called it the "beginning of the greatest sorrows in England". Other regional violence took place between the Bonvilles and Courtenays in the southwest, the Harrington and Stanley families in the northwest, the Earls of Shrewsbury and Wiltshire on the Welsh marches, and between William Tailboys and Ralph, Lord Cromwell in the Midlands. Those disaffected with King Henry centred around York, and as such are often known as Yorkists; those loyal to the king—most of the nobility—are Lancastrian, after the royal dynasty.

In 1455 the king recovered his sanity and Somerset was freed but peace remained elusive and, in May, political tension became open warfare. Henry summoned a council to assemble in Leicester. In response, the Yorkists complained to him of the "doubtes and ambiguitees [and] jealousie" spread by their enemies, and several chroniclers support the view that Somerset was turning the king against York. He and the Nevilles reacted swiftly and brutally, perhaps fearing imminent arrest. In a pre-emptive strike, they ambushed the small royal army—mainly comprising just Henry's household—at the First Battle of St Albans on 22 May. The confrontation was brief with few fatalities, but among whom were Somerset, Henry, Earl of Northumberland and Thomas, Lord Clifford. They were three of the King's most loyal and powerful supporters, and the first two were personal enemies of York and the Nevilles. The clash has been described as closer to a series of targeted assassinations to a fully fledged battle. Henry was captured by the Yorkists, who once again controlled the government. York became Protector a second time, albeit only until February 1456, when the king felt he had enough support among the lords to rule alone.

Four years of peace followed. By 1459, despite the king's efforts at reconciliation, politics again erupted into civil war. In September 1459, Salisbury, who the previous year had determined to "take the full part" with York, brought a 5,000-strong army from Middleham Castle to meet York at Ludlow. En route they encountered a larger royal force at Blore Heath, which Salisbury defeated. Salisbury's victory was temporary and, in October, the Yorkists were routed at Ludford Bridge. York went into exile in Dublin; Salisbury, Warwick and York's son, Edward of March, took refuge in the English-occupied French town of Calais. They were attainted in the Coventry Parliament soon after.

In May 1460, English politics was again overturned, when the Calais lords returned and entered London the following month. Warwick and March journeyed north and defeated the King's army at the Battle of Northampton on 10 July. Henry was once again a Yorkist prisoner.

And coming there he walked straight on, until he came to the king's throne, upon the covering or cushion on which laying his hand, in this very act like a man about to take possession of his right, he held it upon it for a short time. But at length withdrawing it, he turned his face to the people, standing quietly under the canopy of royal state, he looked eagerly for their applause.